Battery Supply For CD Player

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TV Man

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Joined 2002
#1
Using the TDA1541 DAC we need +5v, -5v & -15v.

Getting + or -5v from a battery is simple enough, but what's the easiest way to get our -15v supply?

Also, the opamps in my player use + & -15v creating the need for a +15v battery supply as well.

It might be easier to simply go with + & -12v for the opamps instead. How would this affect the sound (OPA627), any thoughts?

Thanks
 
#3
Hi,

Yes 10 1.5v batteries is an option. But managing charging for that many batteries is more complex.

I was thinking maybe a 12v and 6v in series, or 2 12v batteries in series, but dropping 9v seems like a lot. Maybe someone has done this and has a simple solution??

Thanks
 
#4
Ive used battery 2 *12v lead acid in series, switching and conventional PSs on my active crossover. What I found was that the high frequency coming through the BB opamp 2134 sounded raspy (vocals) regardless of power supply. So my conclusion in this application was that even a low quality supply was inaudible when used with this device. So now I dont use the active for the high pass.

One option that seemed very workable was the NiMh batteries for power tools: 9, 12, 14 or 18. They have good capacity and you can get a fairly smart charger that will work with all the voltages. Im not sure how well theyd work in a situation were they arent run flat but I think theyve come a long way in terms of avoiding memory. You could always run them flat with a resistor.
 
#5
Fritz said:

One option that seemed very workable was the NiMh batteries for power tools: 9, 12, 14 or 18. They have good capacity and you can get a fairly smart charger that will work with all the voltages. Im not sure how well theyd work in a situation were they arent run flat but I think theyve come a long way in terms of avoiding memory. You could always run them flat with a resistor.
Click to expand...


That is a good idea - except these batteries are absurdly expensive. I mean, even a Ryobi 18V is $59, DeWalt and other brands are $75. the charger isn't cheap either

I bought a few 7ah 12V sealed gel batteries for $7.25 each and a smart harger can be bought for $15 - I think that leaves enough room for a good regulator and a nice heat sink if you have to bring it down from 24V 🙂

I'm currently building the DDAC1543 with these batteries, where I am turning 12V into 5 and 8.5v - seems no big deal and is considerably cheaper than the power tool batteries.

I'm already planning to power my tube amp with a case full of these batteries - I will need 14 of them to get the voltages I need 🙂

Peter


Peter
 
#6
A word of caution, while developing the Battery supplies for the updated Pink Triangle PIP II Pre-Amp & for the Dacapo DAC, I found NiCad batteries to be very noisy – an effect I had never considered – nor heard of (I guess due to the internal chemistry process within NiCad cells).

Have no experience of NiMH in Audio applications, but after the experience with NiCad batteries, I would first investigate their noise performance.

The best solution then (more then 10 years ago) was to use sealed Lead-Acid cells – cheap, relatively easy to charge, long life & low noise.

If your design a Battery supply for a digital product, You could automatically switch to battery bulk / trickle charge after a period of non-activity, by monitoring the Audio data line – as the PT Dacapo design did.
 
#7
Hello all.

I'm planning to feed a Scott Nicon dac with DC from a 12v 7ah lead acid battery.

Assuming the charger is switched off at the wall during listening, is it okay for the dac and charger to be connected simultaneously to the battery?

TIA
 
#10
It might be easier to simply go with + & -12v for the opamps instead. How would this affect the sound (OPA627), any thoughts?
Click to expand...

There is a whole lot of talk over at www.head-fi.org (diy section) of power concerns regarding opamps. The general consensus on the OPA627 (and actually all of the Burr-Brown chips save the low power 134) is that although they run off as little as +-12V it it better to be somewhere between +-12V and +-18V. Many, including myself have had great success with ~15V supplies. However, it is hard to generate 15V from two 12V batteries while it is very easy to generate +-15V from a 24V supply due to rectifying and smoothing.

These may be of help
http://tangentsoft.net/audio/opamp-ps.html
http://tangentsoft.net/audio/opamp-wv.html
granted they are aimed at driving headphones but the theory is the same.

Hope this helps

Milo
 
#14
Will a battery powered DAC cause damage when the batteries run down?

I am building a battery powered DAC- It uses 20 x NiMHd cells to make up 5 different supply rails:

+/- Analogue
+ Digital
+PLL
+Clock

My rather messy prototype sounds great! The only problem is that when the batteries start to run down I get distortion. At this stage I know it is time to do a recharge. I have devised a circuit to monitor battery voltage and light LEDs when the voltage becomes too low, but the beauty of my existing DAC design is in its simplicity. I would like to keep my design minimalist, but I am concerned that the distortion might cause damage to the rest of my hi-fi set:

Q. Is it likely that the distortion could cause damage? e.g. could it cause clipping and damage my tweeters if am am playing music at loud volume when the juice runs out?
 
#15
Oli,
I am running my PCM1704 dac on NiMh's and yes it starts to distort a bit when the voltage drops below 4.5 volts.

At around 3.8 it is getting bad but I don't think it hurts the rest of my gear more then it hurts my ears so it is kind of self adjusting.

Eventhough the batteries are better then many standard supplies I also agree with JohnW that the batteries are not dead quite and will benefit from a bit of filtering and/or noise reduction.
 
#16
Thanks for your experience with low batteries and distortion

A 8,

Thanks for your experience with low batteries and distortion-

I will save myself the hassle of building the low battery sensor circuit and make the design real minimalist!

I agree that NiCads are noisy- there is some interesting information on the TNT Audio website concerning supply noise- Various regulators and battery supplies are analysed.

I use 220uF OSCONs with my NiCads and I am very pleased with the result- I could probably do a little better with shunt regulators.

I suppose the nature of the noise is also important- i.e. is it audiable?
 
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